Responsive strategies of three sympatric small rodents to the altitudinal effects on microhabitats

This study evaluated the effects of altitudinal gradients on small-rodent populations and microhabitat conditions. We selected three altitudinal bands: lowland, mid-land, and highland. We captured three small-rodent species, the striped field mouse (Apodemus agrarius), the Korean field mouse (A. peninsulae), and the red-backed vole (Myodes regulus). A. agrarius preferred microhabitats with dense ground vegetation and sparse mid-story vegetation, basal area, downed trees, and stone coverage. A. peninsulae utilized ground vegetation, overstory vegetation, and downed trees. M. regulus occupied microhabitats with abundant stone coverage and little ground vegetation coverage. Ground vegetation coverage was higher in the mid-land. The lowland was characterized by high understory vegetation, bulky downed trees, and high stone coverage. A. agrarius mostly occupied the mid-land, whereas A. peninsulae and M. regulus mainly inhabited the lowland. Our results show that each small-rodent species had its own strategy for utilizing the key habitat factors in altitudinally affected microhabitats and for reducing competition among the populations. This finding contributes to improving knowledge of the ecological altitudinal features of microhabitat conditions, as well as the altitudinal distributions and abundances of three small-rodent species.

Cascade effects of slope gradient on ground vegetation and small-rodent populations in a forest ecosystem

In this study, we set out to determine the cascade effects of slope gradient on ground vegetation and small-rodent populations in a forest ecosystem. We focused on two forest-dwelling small rodents with different habitat requirements, the striped field mouse Apodemus agrarius (preferring dense ground vegetation) and the Korean field mouse A. peninsulae (dense forest and woodland). The study area comprised natural deciduous forests and Japanese larch Larix kaempferi plantations in South Korea. The abundance of A. agrarius but not that of A. peninsulae was related to slope gradient. There was a negative effect of slope gradient on ground vegetation coverage and a positive effect of ground vegetation on A. agrarius populations. Our results highlight that the population of A. agrarius was indirectly influenced by the negative effects of slope gradient on ground vegetation. Slope gradient can, therefore, be a limiting factor in the microhabitats occupied by small rodents. This study reveals a critical role for slope gradient since it can modify not only microhabitat conditions, but also small-rodent populations, and this finding can contribute to improved microhabitat management.

Influence of vegetation area and edge length on mammals in urban woods

We investigated the relationships between vegetation area, edge length, and mammals in the urban woods of Daejeon Metropolitan City, South Korea. The vegetation patches included in this study varied from 2.1 to 501.0 ha in size. Surveys were conducted monthly between February and October 2015, with a survey route measuring 1 km in length and 10 m width established in each forest patch. Field signs of 14 species of mammals were recorded in the 33 chosen forest patches over the course of the study period, and the number of species in each patch varied from 2 to 11. Mammal species richness was positively correlated with vegetation area, and field sign frequency was positively correlated with vegetation area and negatively correlated with edge length. The field sign frequencies of large moles Mogera robusta, Siberian chipmunks Tamias sibiricus, leopard cats Prionailurus bengalensis, Korean hares Lepus coreanus, water deer Hydropotes inermis, and wild boars Sus scrofa were positively correlated with vegetation area. Moreover, that of large moles, leopard cats, Korean hares, and water deer were negatively correlated with edge length. Remnant vegetation area and edge length are the primary determinants of mammal species richness and field sign frequency in urban woods, highlighting the importance of vegetation patch size for mammal conservation in fragmented urban landscapes.

Behaviors and body weight of suckling piglets in different social environments

OBJECTIVE

This study was conducted to characterize the behaviors and the body weight of suckling piglets in different social environments.

METHODS

Two groups of sows and suckling piglets housed either in individual farrowing crates in separate pens (1.8×2.4 m, the control group) or in groups of three sows with their piglets in farrowing crates in a large common enclosure (5.4×2.2 m, the treatment group) were observed with the aid of video technology for 9 consecutive hours on days 1, 2, and 3, after mixing.

RESULTS

Suckling, agonistic, and elimination behaviors of suckling piglets were significantly higher in the control group than in the treatment group. Inactive behavior was higher in the treatment group than in the control group. Most of the effects of the social environment on the suckling piglets seem to be the result of large reductions in behaviors and body weight for piglets switching from high activity to low activity. Moreover, suckling behavior and birth body weight were highly correlated with body weight at the end of the test.

CONCLUSION

The social environment that resulted from mixing, thus, had significant effects on the behavior and body weight of suckling piglets, and behavioral characteristics, therefore, should be considered when making improvements to the husbandry and care methods used in swine production.

Influence of tree thinning on the abundance of mammals in a Japanese larch Larix kaempferi plantation

We examined the influence of tree thinning on the abundance of mammals in a Japanese larch Larix kaempferi plantation in Mt Gariwang, Pyeongchang, South Korea. In 2014 and 2015, from April to October, we recorded the presence of tracks as a proxy for abundance, for the following seven mammalian species: Korean hare Lepus coreanus, raccoon dog Nyctereutes procyonoides, Siberian weasel Mustela sibirica, Eurasian badger Meles meles, water deer Hydropotes inermis, roe deer Capreolus pygargus, and wild boar Sus scrofa. We also assessed how the intensity of tree thinning affected vegetation cover; there were significant differences in number of standing trees, basal area, coverage of vegetation layers, and number and volume of downed trees among the control, moderately thinned, and intensively thinned stands. We found significant differences in the abundance of tracks among the stands for three mammal species. In four mammal species, the abundance of track was significantly correlated with volume of downed trees, coverage of ground vegetation, number of downed trees, and number of standing trees, according to stepwise analysis. The presence and abundance of mammals is linked to habitat variables and forest managers should consider how habitat modifications will affect wildlife.

Behavioral Characteristics of Weaned Piglets Mixed in Different Groups

With regard to animal welfare concerns, behavioral information of weaned and mixed piglets is great interest in swine production. The aim of this study was to demonstrate the change in behavior of weaned piglets over time in two different groups (littermates and piglets from different litters) after mixing. Two weaned groups of piglets (72 individuals in all) housed either with littermates or with foreign piglets (6 individuals in 1.8 m×1.4 m pens, 28°C±1°C temperature) were observed with the aid of video technology for 9 consecutive hours on days 1, 2, and 3 after mixing. The behaviors of the weaned piglets in the control and treatment groups were significantly different among the days after mixing. Piglets were, however, more active and aggressive in the groups with foreign piglets. This study reveals a lower level of agonistic behavior in groups of piglets that came from the same litter.

Effects of Mixing on the Aggressive Behavior of Commercially Housed Pigs

In this study, we investigated the effects of mixing on the aggressive behavior of commercially housed pigs. The behavioral patterns of 36 groups of pigs (a total of 360 animals) were observed over 3 consecutive days directly after weaning (25±1.2 days of age), and 25 and 50 days later with the aid of video technology. Fight latency and total duration and frequency of fighting were significantly different among the age groups. The aggressive behaviors decreased in 75-day old pigs if compared to 25- and 50-day old animals. Moreover, dominance index (DI) was higher in 25-day old and lower in 75-day old pigs. A comparison of dominant (DI>0) and submissive (DI<0) pigs showed significant differences (p<0.05) for major aggressive behaviors in all age groups. Dominant pigs were involved in more aggressive interactions, had longer fights, and initiated more fights than submissive pigs. Post-mixing aggressive behavior was altered by previous experience of mixing. Aggressive behavior and DI are suitable methods for analyzing the effects of mixing on commercially housed growing pigs.